Circumstantial Attributive Clause With Assignment?

the living area	extends	from the lounge room to the billiard room
Carrier	Process: circumstantial	circumstantial Attribute

the living area	has been extended	from the lounge room to the billiard room
Carrier	Process: circumstantial	circumstantial Attribute

the living area	has been extended	from the lounge room to the billiard room	by the new owners
Carrier	Process: circumstantial	circumstantial Attribute	Attributor

the new owners	have extended	the living area	from the lounge room to the billiard room
Attributor	Process: circumstantial	Carrier	circumstantial Attribute

However, ASSIGNMENT is a system that is restricted to intensive relations. Halliday & Matthiessen (2014: 288):

Both ‘identifying’ and ‘attributive’ clauses of the ‘intensive’ kind have the option of ASSIGNMENT: they may be configured with a third participant representing the entity assigning the relationship of identity of attribution – for example, they in they made Mary the leader and they made Mary happy. In the case of ‘identifying’ clauses, this is the Assigner; in the case of ‘attributing’ clauses, this is the Attributor. In a ‘receptive’ clause, this participant may be left implicit.

If this is true, then it suggests a different analysis of the 'assigned' clauses above.  Given what would be the unmarked present tense, these clauses are material:

• the new owners are extending the living area from the lounge room to the billiard room, not
• the new owners extend the living area from the lounge room to the billiard room.

On this basis, the analyses are reinterpreted as follows:

the living area	extends	from the lounge room to the billiard room
Carrier	Process: relational	circumstantial Attribute

the living area	has been extended	from the lounge room to the billiard room
Goal	Process: material	Extent

the living area	has been extended	from the lounge room to the billiard room	by the new owners
Goal	Process: material	Extent	Actor

the new owners	have extended	the living area	from the lounge room to the billiard room
Actor	Process: material	Goal	Extent